Systematic review protocol of aetiology of mechanical bowel obstruction in low-and-middle income countries: Has anything changed in the last two decades?

The aetiology of mechanical bowel obstruction exhibits significant variability based on geographical location and age. In high-income countries, postoperative adhesions and hernias are frequently cited as the primary causes, whereas in low- and middle-income countries (LMCIs), hernias take precedence. Speculation exists within the surgical community regarding whether this trend has evolved in LMCIs. To address this knowledge gap, our study aims to conduct a systematic review of existing literature, focusing on understanding the most prevalent causes of mechanical bowel obstruction in both pediatric and adult populations within LMCIs, providing valuable insights for surgical practice. This protocol was designed and written according to the guidelines of the Preferred Reporting Items for Systematic Review and Meta-analysis Protocol 2015 (PRISMA-P 2015) statement. However, the results of the systematic review will be reported following the Preferred Reporting Items for Systematic Review and Meta-analysis (PRISMA) statement. We will consider studies published in English and French between 2002 and 2022 that reported on the aetiology of mechanical bowel obstruction in any age group in low- and middle-income countries. We will conduct a literature search using Ovid MEDLINE, Ovid Embase, CINAHL on EBSCO and Web of Science databases employing relevant subject headings, keywords and synonyms, which will be combined using Boolean operators to refine the search results. A hand search of references of retrieved literature will be conducted. The retrieved articles will be imported into Zotero for de-duplication. The resulting set of titles and abstracts will be uploaded to Rayyan (an AI-assisted online systematic review tool), where they will be double-checked to identify articles eligible for inclusion. Two independent reviewers will screen articles to be included and disagreement will be resolved by discussion or by a third reviewer as a tie-breaker. Also, data extraction will be done by one reviewer and confirmed by another. Critical appraisal to assess the quality of the included studies will be carried out by two independent reviewers using the Joanna Briggs Institute (JBI) tools. We anticipate that the eligible studies will be quite heterogeneous in terms of their design, outcomes of interest, populations and comorbidities. Therefore, resmay be synthesised descriptively without meta-analysis using charts, graphs and tables. Where possible, we will conduct a sub-analysis using conceptual frameworks based on age, WHO regions and continents.


Introduction
Acute bowel obstruction stands as a common surgical emergency, particularly encountered by surgical trainees in the Emergency Department (ED).It comprises 3% of all emergency admissions and contributes to 15% of cases involving acute abdominal pain [1].The majority of these cases (more than two-thirds) are mechanical small bowel obstructions [2], characterized by a sudden onset of symptoms such as vomiting, abdominal pain, distension, and constipation.Prompt diagnosis and treatment are crucial, as delayed intervention may lead to strangulation and/or gangrene [1][2][3][4][5].This surgical pathology poses a significant challenge, especially in low-and middle-income countries (LMICs), where the majority of patients are seen in secondary care settings.The associated morbidity and mortality are notably higher in LMICs, reaching reported rates of 5-13.5% [3,5,6].Recognizing the diverse causes of mechanical bowel obstruction is essential for timely and accurate diagnosis, ensuring appropriate therapeutic measures are undertaken.
Mechanical bowel obstruction has many causes.Post-operative adhesions have been reported as one of the most common aetiologies.They are reported to occur in approximately 93% of patients who have undergone abdominopelvic surgery [1].The most commonly observed sources of peritoneal adhesions are appendectomy, gynaecological surgery and colorectal surgery [1,3].However, only 5% of these are symptomatic [1].Another important and common cause of bowel obstruction is hernia, such as inguinal, umbilical and incisional subtypes [4].Other aetiologies include volvulus, intussusception, intestinal malignancy, vermiform impaction, Meckel's diverticulum and intestinal tuberculosis [3,4,7].
Despite these various causes of mechanical obstruction, there appears to be a great deal of variation depending on geographical location and age [8].In terms of age, hernia and adhesion as well as anorectal malformation and intussusception have been reported to be the most common causes in adults and children, respectively [1,3,8,9].Geographically, postoperative adhesions have been documented as the most common aetiology of mechanical bowel obstruction in high-income countries (HICs).This may be due to the high volume of abdominal surgery [8,9].In contrast, many studies have reported hernias as the most common aetiology in LMICs [1,4,8,10].
Whether there has been a change in this trend in LMICs is a matter of speculation in the surgical community.Although there are international empirical studies that have evaluated the changing trend in the causes of mechanical bowel obstruction in different countries of the LMICs, the results of these studies are contradictory [2][3][4][5]7,10,11].While some showed that hernia remained the most common cause in LMICs [1,3,4,8], others showed changing patterns towards postoperative adhesions [2,5,11].Therefore, this review aims to consolidate evidence, guiding safe surgical practices.Many studies on this topic are retrospective with low evidence levels, prompting a comprehensive review for higher-quality data.Notably, there's a lack of systematic reviews across low-and middle-income countries (LMICs) for understanding the causes of mechanical bowel obstruction, leaving a critical knowledge gap for timely diagnosis and management in emergencies.This study addresses this gap by systematically reviewing literature, focusing on predominant causes in pediatric and adult populations in LMICs.Given the high morbidity and mortality, understanding common causes is crucial for improving outcomes, aiding surgical trainees in prompt decision-making amid health system challenges.

Methodology
This protocol was designed and written according to the guidelines of the Preferred Reporting Items for Systematic Review and Meta-analysis Protocol 2015 (PRISMA-P 2015) statement [12] (S1 Checklist).This framework prescribes best practices for the development and reporting of systematic review protocols.The review has been registered in PROSPERO, an international digital repository for the pre-registration of systematic reviews, identified by CRD42023468901.There are several benefits to registering the research protocol, including avoiding redundant research efforts, reducing bias, and increasing the overall transparency of the review process.The results of the systematic review will be presented following the Preferred Reporting Items for Systematic Review and Meta-analysis (PRISMA) statement [13].Should any deviations from the established protocol occur during the conduct of the review, these will be duly accounted for in the final publication.

Eligibility
We will consider studies published between 2002 and 2022 in low-and middle-income countries (LMICs) that are either case series, case-control or cohort studies reporting on the aetiology of mechanical small bowel obstruction in any age group.Studies must be published in either English or French.We will exclude animal studies, studies with different designs, those published in high-income countries, those outside the specified date range, or those published in languages other than English or French.Should our manuscript be accepted for publication, an updated literature search will be conducted by employing the peer-review study methodology.This will prevent missing important new evidence.

Data sources
We will conduct a literature search using Ovid MEDLINE, Ovid Embase, CINAHL on EBSCO and Web of Science databases.Our search strategy will include the use of relevant subject headings, keywords and synonyms, which will be combined using Boolean operators to refine the search results.To focus our search on low-and middle-income countries (LMICs), we will use the ScHARR geographic filter [14] to exclude studies from non-LMIC countries.In addition, we will manually search the reference lists of the included studies to find additional relevant articles.

Search strategy
A search strategy was developed using the key terms 'small bowel obstruction', 'lower-middleincome countries' and 'aetiology'.The MEDLINE search strategy, adapted for other databases, is shown in Fig 1.

Study selection and data extraction
The retrieved references will be imported into Zotero for de-duplication.The resulting set of titles and abstracts will be uploaded to Rayyan [15] (an AI-assisted online systematic review tool), where they will be double-checked to identify articles eligible for inclusion.These will then be exported to Zotero for reference management and full-text screening.Studies that do not meet the eligibility criteria at this stage will be excluded, with reasons documented.This process is carried out by two independent authors.Disagreement will be resolved by discussion or by a third reviewer as a tie-breaker.
A data extraction form adapted from the Joanna Briggs Institute (JBI) will be used for data extraction.The variables to be extracted from the included studies are described in Table 1.The data extraction form will be pre-tested independently by two reviewers using randomly selected articles.This will help to identify gaps that can then be used to refine the form.Data extraction will be carried out by two reviewers; reviewer A will extract the data, while reviewer B will check the accuracy of the extracted data.

Risk of bias assessment
Critical appraisal to assess the quality of the included studies will be carried out by two independent reviewers.We will use the Joanna Briggs Institute (JBI) tools [16] for each study design (case series, case-control, cohort) to be included in the review.We chose the JBI tools because they provide tools for a variety of study designs and are a widely used set of tools in systematic reviews.The JBI score is used to rate the quality of each included study as good, fair or poor.The quality rating would not be used to exclude a study from the review.

Data synthesis
We anticipate that the eligible studies will be quite heterogeneous in terms of their design, outcomes of interest, populations and comorbidities.Therefore, results may be synthesised descriptively without meta-analysis.The characteristics of the included studies will be presented in a detailed table.In addition, important findings will be highlighted using charts and graphs.The review synthesis will be based on the major categories of small bowel obstruction aetiologies identified.Where possible, we will conduct a sub-analysis using conceptual frameworks based on age, WHO regions and continents.

Discussion
The proposed systematic review aims to examine the existing literature on the causes of mechanical bowel obstruction in LMICs from 2002 to 2022, with a particular interest in the common aetiology to guide safe surgical practice.Identifying the common causes of mechanical bowel obstruction in the context of fragile health systems in LMICs over the last two decades is critical to halting the unacceptably high mortality associated with this surgical condition.This review has the potential to provide surgical trainees with scientific evidence to raise a high index of suspicion for prompt diagnosis in patients presenting with acute abdomen to the emergency department.Making the correct diagnosis would enable surgeons to offer appropriate interventions to patients in need, regardless of the limited diagnostic modalities in LMICs.
The review would identify gaps that could be potentially explored through further research by scientists to better understand the aetiology of mechanical bowel obstruction in LMICs.In addition, the evidence to be synthesised may also assist the academic community in communicating new knowledge, as well as policymakers in formulating appropriate policies that could improve surgical needs and outcomes.
The review will have some limitations.Because it is limited to LMICs, a real-time comparison with the more recent common aetiology of mechanical bowel in HICs would be difficult.However, the robust health systems in HICs, including advanced diagnostic modalities, can prevent missed diagnoses and prompt treatment.Furthermore, the aetiological pattern of mechanical bowel obstruction in this setting is unlikely to have changed, given the recent incontrovertible evidence from empirical studies.Furthermore, due to a lack of funding, librarians could not be consulted for expert input, which may have resulted in some important empirical studies being overlooked.Despite these limitations, this review, when completed,

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Reported causes of mechanical small bowel obstruction (up to five) https://doi.org/10.1371/journal.pone.0295477.t001 has great potential to add to the body of knowledge, particularly in the surgical community, to improve outcomes.It will also shape future research in the gaps that remain to be identified.